Phylogeny and Diversification of Araliales

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9981641Plunkett and Lowry Two investigators, the first a young scientist with expertise in molecular systematics and impressive publications from his dissertation studies and the second an experienced field naturalist and plant monographer, are combining forces to study the large, mostly southern hemisphere plant family Araliaceae and its close relatives, to improve taxonomic classification of the group, construct a framework phylogeny for the genera, and begin to determine the historical biogeography that accounts for the current widespread distribution of these plants. The Araliaceae are the predominantly tropical relatives of the mostly temperate-zone carrot family, the Apiaceae or Umbelliferae. Araliaceae include numerous small (1-25 species) genera, and two huge genera, Schefflera (with ca. 650 described species) and Polyscias (with ca. 150 species). With Apiaceae and the Old World tropical family Pittosporaceae, the Araliaceae constitute the order Araliales, along with four difficult-to-place genera: Aralidium (western Malesia), Griselinia (disjunct in Chile and New Zealand), Melanophylla (Madagascar), and Toricellia (the Himalayas). Traditional morphological characters, useful in species-level discrimination, have proved unreliable in delimiting sublineages within the group, but preliminary DNA sequence data show evidence of resolving the major lineages and many sublineages within Araliales. With extensive samples already accumulated, in large part due to Lowry's personal field collecting and contacts with colleagues worldwide, and to be supplemented with targeted field work in Asia and Australasia, new data will be collected for nuclear and chloroplast genes, in order to assess mutational differences at species, genus, and family levels throughout the group. Selected anatomical, chromosomal, and morphological characters will be integrated to bolster phylogenetic resolution and improve generic classification. With a reliable phylogenetic framework in place, the investigators can begin to unravel the historical pathways of migration and diversification that have resulted in the current distribution of the group. A few aralialean fossils suggest Cretaceous origins for the group, consistent with an early "Gondwanan" distribution pattern, and subsequent expansions on all the southern hemisphere continents. Further insights rely upon successful resolution of the phylogenetic relationships of the genera, in turn upon careful taxonomic sampling of the known geographic and morphological variation in Araliales.